Known arrangements of brakes in wheel heads (see German Patent Application No. 30 13 431.7-21 or U.S. Pat. No. 4,037,694) have internal brake disks non-rotatably secured to the set of teeth of the sun wheel of the reducing gear driven by a differential shaft and external brake disks non-rotatably secured to the set of teeth of the hollow wheel which is steadfastly mounted in its housing, whereby power-assistance means is provided in the carrier of the hollow wheel as a brake pressure annular piston, operated by a pressure medium.
The disadvantages of these usual constructions currently known become evident especially in the production of large series of axles with such wheel heads and in their use in practice. Because of the interchangeable dimensional relationship of the construction parts with regard to each other it has proven difficult to provide for adaptability to changing user requirements (performance, way of brake actuation, maintainance), since it was almost impossible to create any equipment variations with a single, definitely established axle concept. For instance, in the case of the aforementioned hollow wheel with the differential shaft not only the ratio of the reducing gear, but also the effective diameter of the brake disks, the mode of securing the hollow wheel carrier and as a result also the type of power assist are rigidly established. The ratio could not be varied further since the diameter of the hollow wheel was rigidly established. In the case of given larger hollow wheels, disadvantageous diameter ratios D/d of the brake disks also resulted, which means that in certain ranges of the rotation rate these would run erratically and be prematurely damaged or their braking efficiency would be impaired. When for instance, a different hollow wheel carrier became necessary due to a different power-assisting means, the placed available in the housing was not sufficient or the supply of the pressure means in the hollow axle did not suit the arrangement of the brake piston in the carrier of the hollow wheel. Due to such interdependencies not only uneconomical manufacturing- and assembly processes resulted, but also the use and maintainance were impaired.